This invention relates to safety pressure relief devices and has particular reference to assemblies of such devices incorporating arrester bars.
One known type of safety pressure relief device is a reverse buckling device. Reverse buckling discs have been proposed in British Patents Specifications Nos. 1 355 486 and 1 444 206 and the devices described in those specifications have been found to work extremely satisfactorily. The devices described in the above specifications, which are referred to as reverse buckling pressure relief discs, utilise discs having a central portion which is convex on one side and concave on the other and which is held between two annular members around an edge region of the disc. In use the pressure relief apparatus incorporating the disc and annular members is located upon a vessel with the convex side of the disc facing towards the interior of the vessel so as to be in direct contact with the fluid contained within the vessel. When the fluid pressure within the vessel reaches a predetermined limit the curvature of the disc is reversed and the disc pulls free from the annular members and is released. Because the disc is completely released from the holder the entire area of the holder is available for venting excess pressure. It has been found, however, that in many cases it is desirable to provide an arrester bar to catch the disc, which is blown out by the excess pressure to prevent the disc causing damage downstream. If the arrester bar is positioned correctly, and this is a matter for simple experiment, the disc is found to wrap itself around the arrester bar and is firmly held in position even after the excess pressure has been vented. Heretofore the arrester bars have been provided in a separate item which is attached to the reverse buckling assembly as an option.